1. Field of the Invention
The present invention relates to detection systems for detecting arcing faults occurring in the electrical circuits, and in particular, to a detection system for detecting and preventing arcing faults in the electrical switchboards in ungrounded or high-resistance grounded power distribution systems.
2. The Prior Art
An arcing fault in an electrical switchboard can burn the switchboard and propagate the arc into adjacent switchboards or eject hot plasma into the manned spaces. These arcing faults are caused by dirt, moisture, loose connections, or the like and are essentially high-impedance phase-to-phase faults that are not quickly detected by modern day circuit breakers.
The Johns Hopkins University, Applied Physics Laboratory has developed an arc fault detection (AFD) system for detecting and preventing arcing faults in switchboards. The AFD system detects arcing faults within switchboards using optical and differential pressure sensors installed in the switchboards After receiving signals from the optical and differential pressure sensors, the control unit of the AFD system trips open the appropriate upstream circuit breaker. However, it has been found that in many switchboards, optical and differential pressure sensors cannot be installed because of inadequate space, and because of the presence of ventilating louvers and wide openings for cable entry. Such ventilating louvers and wide openings for cable entry can prevent pressure build-up inside the switchboards, making differential pressure sensors, and hence the AFD system, ineffective.